Aptitude testing

ABSTRACT

A method of assessing the cognitive aptitude of a subject to a predetermined task, the method including the steps of: (i) presenting to the subject a group of cognitive tasks; (ii) detecting brain response signals from the subject during presentation of the group of cognitive tasks; (iii) calculating SSVEP amplitude, phase and/or coherence responses from the brain response signals; and (iv) comparing the SSVEP responses to known SSVEP responses obtained from individuals with high and/or low aptitudes to the predetermined task in order to assess the subject&#39;s aptitude for the predetermined task.

FIELD OF THE INVENTION

The present invention relates generally to the field of aptitudetesting, including apparatus and methods for testing the aptitude ofsubjects to mental tasks and assessing subjects thinking style.

BACKGROUND OF THE INVENTION

Existing commonly-used aptitude tests attempt to measure a subject'scurrent abilities using a standardised test appropriate to the subject'sage, language, culture and educational background. The tests do notnecessarily identify potential aptitude in subjects who do not meet abasic requirement of the tests such as a particular educationalbackground or for whom no standardised test exists or is appropriate.For example, as existing tests require a minimum level of knowledgebefore aptitude can be assessed, those subjects with natural abilitiesnot meeting the minimum requirements would generally not be identifiedas potential candidates. Furthermore, minorities may consider certaintests to be unfair and discriminatory. There is a need for a new testwhich can be used to assess potential aptitude as well as currentaptitude levels.

Aptitude and thinking style are closely related and thus a test that canidentify aptitude can also be used to identify a subject's thinkingstyle. Knowledge of a subject's thinking style can also be used toidentify the optimum teaching and training approach for the subject.

U.S. Pat. Nos. 4,955,938 and 5,331,969 (the contents of which are herebyincorporated herein by reference) disclose techniques for obtaining asteady state visually evoked potential (SSVEP) from a subject. Thesepatents disclose the use of Fourier analysis in order to rapidly obtainthe SSVEP's and changes thereto.

SUMMARY OF THE INVENTION

It is now appreciated that these techniques can be utilized to measurebrain activity and assess the aptitude of an individual.

More particularly the invention provides a method of assessing thecognitive aptitude of a subject to a predetermined task, the methodincluding the steps of:

-   -   (i) simultaneously presenting to the subject one of a group of        cognitive tasks and a visual flicker;    -   (ii) detecting brain response signals from the subject during        presentation of said cognitive task and visual flicker;    -   (iii) calculating amplitude, phase and/or coherence of SSVEP        responses elicited by the visual flicker from said brain        response signals; and    -   (iv) comparing said SSVEP responses to known SSVEP responses        obtained from individuals with high and/or low aptitudes to said        predetermined task in order to assess the subject's aptitude for        said predetermined task.

The invention also provides an apparatus for assessing the cognitiveaptitude of a subject to a predetermined task, the apparatus including:

-   -   (i) means for simultaneously presenting to the subject one of a        group of cognitive tasks and a visual flicker;    -   (ii) means for detecting brain response signals from the subject        during presentation of said cognitive task and visual        flicker; (iii) means for calculating amplitude, phase and/or        coherence of SSVEP responses elicited by the visual flicker from        said brain response signals; and    -   (iv) means for comparing said SSVEP responses to known SSVEP        responses obtained from individuals with high and/or low        aptitudes to said predetermined task in order to assess the        subject's aptitude for said predetermined task.

The present invention can utilise Steady State Probe Topology (SSPT), abrain imaging technique based on the brain's response to a continuoussinusoidal visual flicker or the SSVEP to examine changes in theactivity in various brain regions while an individual undertakes anumber of cognitive tasks. The cognitive aptitude will be indicated byspecific changes in SSVEP amplitude, phase and coherence during a givencognitive task. The changes in SSVEP amplitude, phase and coherence canalso indicate different thinking styles associated with differentpatterns of brain activity. Subjects that score high, on a test ofanalytical thinking show greater left hemisphere phase advance that isinterpreted as greater activation of this area during the analyticaltask. By contrast, subjects that score low on the test of analyticalthinking do not show this pattern. In addition, subjects that score highon a test of holistic thinking show greater SSVEP phase advance at righthemisphere sites. These results are consistent with neuropsychologicalresearch indicating a specialised role for the left hemisphere inanalytical thinking and the right hemisphere for holistic thinking.

More generally, SSVEP can be used to identify aptitude in specificcognitive domains known to be associated with performance and trainingaptitude. For example, trainee aircraft pilots need aptitude invisualizing their environment in three dimensions. A test for thisability could involve SSVEP measurements while the subject undertakesthe Mental Rotation Task where they are required to rotate images ofthree dimensional shapes. Specific changes in SSVEP amplitude, phase andcoherence are associated with a high aptitude for this task and thesechanges may be used to identify individuals with a high ability tomanipulate three dimensional images. Studies undertaken by the inventorreveal that individuals with a high aptitude for the manipulation ofthree dimensional images exhibit a greater phase advance at leftprefrontal cortical sites and reduced coherence between central andparietal cortical sites. By contrast, subjects with a high ability showincreased SSVEP coherence between right prefrontal and central sitesduring the time that the image was held in short term memory withoutmanipulation.

More particularly, the techniques of the invention can be used in anumber of different fields including:

-   -   (i) identifying cognitive aptitude in specific domains;    -   (ii) identifying an individual's thinking style and hence the        optimum teaching/training approach;    -   (iii) identifying the suitability of an individual for specific        training; and    -   (iv) identifying the suitability of an individual for specific        employment.

The changes in SSVEP amplitude, phase and/or coherence can be anincrease or decrease. Also, the magnitude of the change may vary fromcase to case. One way of determining whether there has been asignificant change in SSVEP amplitude, phase and/or coherence is byreference to statistical analyses where a change is regarded assignificant at the p<0.05 level where p represents the probability of aType 1 statistical error (i.e. wrongly rejecting the null hypothesis).Statistical significance can be tested using a number of methodsincluding student's t-test, Hotellig's T2 and the multivariatepermutation test. For a discussion of these methods used to analyse theSSVEP see Silberstein R. B., Danieli F., Nunez P. L. (2003)Frontoparietal evoked potential synchronisation is increased duringmental rotation. Neuroreport, 14:67-71, Silberstein R. B., Farrow M. A.,Levy F., Pipingas A., Hay D. A., Jarman F. C. (1998). Functional brainelectrical; activity mapping in boys with attention deficithyperactivity disorder. Archives of General Psychiatry 1998; 55:1105-12.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic diagram of a system of the invention;

FIG. 2 is a schematic plan view showing in more detail the manner inwhich visual flicker signals are presented to a subject;

FIG. 3 is a schematic view showing one of the half silvered mirrors andLED array;

FIG. 4 diagrammatically illustrates SSVEP phase distribution for asubject with high analytical aptitude;

FIG. 5 diagrammatically illustrates SSVEP phase distribution where thesubject has a low analytical aptitude;

FIG. 6 diagrammatically illustrates SSVEP phase distribution forsubjects with high holistic thinking capacity;

FIG. 7 diagrammatically illustrates SSVEP phase distribution forsubjects with low holistic thinking capacity;

FIG. 8 diagrammatically illustrates SSVEP coherence at frontal sites forsubjects having high verbal IQ; and

FIG. 9 diagrammatically illustrates SSVEP coherence in subjects havinghigh conceptual and visualisation skills.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 schematically illustrates a system 20 for determining theresponse of a subject 6 to a cognitive task which can be presented tothe subject 6 on a video screen 1 and loudspeaker 11. The systemincludes a computer 2 which controls various parts of the hardware andalso performs computation on signals derived from the brain activity ofthe subject 6, as will be described below. The computer 2 also holds thecognitive task which can be presented to the subject 6 on the screen 1and/or through the loudspeaker 11.

The subject 6 to be tested is fitted with a helmet 7 which includes aplurality of electrodes for obtaining brain electrical activity fromvarious sites on the scalp of the subject 6. The helmet includes a visor8 which includes half silvered mirrors 17 and 18 and LED arrays 19 and21, as shown in FIG. 2. The half silvered mirrors are arranged to directlight from the LED arrays 19 and 21 towards the eyes of the subject. TheLED arrays 19 and 21 are controlled so that the light intensitytherefrom varies sinusoidally under the control of control circuitry 5.The control circuitry 5 includes a waveform generator for generating thesinusoidal signal. The circuitry 5 also includes amplifiers, filters,analogue to digital converters and a USB interface for coupling thevarious electrode signals into the computer 2.

The system also includes a microphone 9 for recording voice signals fromthe subject 6. The microphone 9 is coupled to the computer 2 via amicrophone interface circuit 10. The system also includes a switch 4which can be manually operated by the subject as a part of the responseto the cognitive task. The switch 4 is coupled to the computer 2 via aswitch interface circuit 3.

The computer 2 includes software which calculates SSVEP amplitude phaseand/or coherence from each of the electrodes in the helmet 7.

Details of the hardware and software required for generating SSVEP arewell known and need not be described in detail. In this respectreference is made to the aforementioned United States patentspecifications which disclose details of the hardware and techniques forcomputation of SSVEP. Briefly, the subject 6 views the video screen 1through the visor 8 which delivers a continuous background flicker tothe peripheral vision. The frequency of the background flicker istypically 13 Hz but may be selected to be between 3 Hz and 50 Hz. Brainelectrical activity will be recorded using specialised electronichardware that filters and amplifies the signal, digitises it in thecircuitry 5 where it is then transferred to the computer 2 for storageand analysis. SSPT is used to ascertain regional brain activity at thescalp sites using SSPT analysis software.

The cognitive tasks are presented on the video screen 1 and/or via theloudspeaker 11. The subject 6 is required to make a response that maycomprise a button push on the switch 4 and/or a verbal response which isdetected by the microphone 9. The topographic distribution of the SSVEPamplitude, SSVEP phase and SSVEP coherence during the performance of thecognitive tasks can be correlated with the aptitude and thinking styleof the subject. The microphone 9 generates audio signals which areamplified, filtered and digitised via the interface 10 and stored assound files on the computer 2. This enables the timing of the verbalresponses to be determined within an accuracy of say 10 microseconds.Alternatively, the subject may respond to the cognitive task via a motorresponse such as a button push via the switch 4. In all cases, theprecise timing of all events presented to the subject 6 are preferablydetermined with an accuracy of no less than 10 microseconds.

As mentioned above, the visor 8 includes LED arrays 19 and 21. In oneembodiment, the light therefrom is varied sinusoidally. An alternativeapproach utilises pulse width modulation where the light emittingsources are driven by 1-10 Khz pulses where the pulse duration isproportional to the brightness of the sight emitting sources. In thisembodiment, the control circuitry 5 receives a digital input stream fromthe computer 2 and outputs pulse width modulated pulses at a frequencyof 1-10 Khz. The time of each positive going zero-crossing from thesinusoidal stimulus waveform is determined to an accuracy of 10microsecond and stored in the memory of the computer 2.

Brain electrical activity is recorded using multiple electrodes inhelmet 7 or another commercially available multi-electrode system suchas Electro-cap (ECI Inc., Eaton, Ohio USA). The number of electrodes isnormally not less than 16 and normally not more than 256, and istypically 64.

Brain activity at each of the electrodes is conducted to the controlcircuitry 5. The circuitry 5 includes multistage fixed gainamplification, band pass filtering and sample-and-hold circuitry foreach channel associated with an electrode of the helmet.Amplified/filtered brain activity is digitised to 16 bit accuracy at arate not less than 300 Hz and transferred to the computer 2 for storageon hard disk. The timing of each brain electrical sample together withthe time of presentation of different components of the cognitive taskare also registered and stored to an accuracy of 10 microseconds.

SSVEP Amplitude, Phase and Coherence

The digitised brain electrical activity (EEG) together with timing ofthe stimulus zero crossings enables calculation of the SSVEP from therecorded EEG or from EEG data that has been pre-processed usingIndependent Components Analysis to remove artefacts and increase thesignal to noise ratio. [Bell A. J. and Sejnowski T. J. 1995. AnInformation Maximisation Approach to Blind Separation and BlindDeconvolution, Neural Computation, 7, 6, 1129-1159; T-P. Jung, S.Makeig, M. Westerfield, J. Townsend, E. Courchesne and T. J. Sejnowskik,Independent Component Analysis of Single-Trial Event-Related PotentialHuman Brain Mapping, 14(3):168-85, 2001.]

Calculation of SSVEP amplitude and phase for each stimulus cycle can beaccomplished using Fourier techniques using equations 1.0 and 1.1 below:

$\begin{matrix}{{a_{n} = {\frac{1}{S\;\Delta\;\tau}{\sum\limits_{i = 0}^{S - 1}{{f\left( {{n\; T} + {i\;\Delta\;\tau}} \right)}\;{\cos\left( {\frac{2\;\pi}{T}\left( {{n\; T} + {i\;\Delta\;\tau}} \right)} \right)}}}}}{b_{n} = {\frac{1}{S\;\Delta\;\tau}{\sum\limits_{i = 0}^{S - 1}{{f\left( {{n\; T} + {i\;\Delta\;\tau}} \right)}\;{\sin\left( {\frac{2\;\pi}{T}\left( {{n\; T} + {i\;\Delta\;\tau}} \right)} \right)}}}}}} & {{Equation}\mspace{14mu} 1.0}\end{matrix}$

Where a_(n) and b_(n) are the cosine and sine Fourier coefficientsrespectively. n represents the nth stimulus cycle, S is the number ofsamples per stimulus cycle (16), Δτ is the time interval betweensamples, T is the period of one cycle and f(nT+iΔτ) is the EEG signal(raw or pre-processed using ICA).

$\begin{matrix}{{{SSVEP}_{amplitude} = \sqrt{\left( {a_{n}^{2} + b_{n}^{2}} \right)}}{{SSVEP}_{phase} = {a\;{\tan\left( \frac{b_{n}}{a_{n}} \right)}}}} & {{Equation}\mspace{14mu} 1.1}\end{matrix}$

Amplitude and phase components can be calculated using either singlecycle Fourier coefficients or coefficients that have been calculated byintegrating across multiple cycles.

Two types of coherence functions are calculated from the SSVEP sine andcosine Fourier coefficients while subjects undertake the cognitive task.One will be termed the SSVEP Coherence (“SSVEPC”) and the other, EventRelated SSVEP Coherence (“ER-SSVEPC”).

SSVEPC

The SSVEP sine and cosine coefficients can be expressed as complexnumbersC_(n)=(a_(n),b_(n))where a_(n) and b_(n) have been previously defined.

The nomenclature is generalised to take into account multiple tasks andmultiple electrodes.C_(g,e,n)=(a_(g,e,n),b_(g,e,n))where

-   -   g=the task number    -   e=the electrode    -   n=the point in time        The following functions are defined:

$\begin{matrix}{{\gamma_{g,{e\; 1},{e\; 2}} = \frac{H_{g,{e\; 1},{e\; 2}}}{T_{g,{e\; 1},{e\; 2}}}}{H_{g,{e\; 1},{e\; 2}} = {\sum\limits_{n = 1}^{n = T}{C_{g,{e\; 1},n} \cdot C_{g,{e\; 2},n}^{*}}}}} & {{Equation}\mspace{14mu} 1.2}\end{matrix}$Where C* is the complex conjugate of C and

$\begin{matrix}{\left. {T_{g,{e\; 1},{e\; 2}} = {\sqrt{\left( {\sum\limits_{n = 1}^{T}{C_{g,{e\; 1},n} \cdot}} \right.}C_{g,{e\; 1},n}^{*}}} \right)\left( {\sum\limits_{n = 1}^{T}{C_{g,{e\; 2},n} \cdot C_{g,{e\; 2},n}^{*}}} \right)} & {{Equation}\mspace{14mu} 1.3}\end{matrix}$The SSVEPC is then given by

$\begin{matrix}{\gamma_{g,{e\; 1},{e\; 2}}^{2} = \frac{{H_{g,{e\; 1},{e\; 2}}}^{2}}{T_{g,{e\; 1},{e\; 2}}^{2}}} & {{Equation}\mspace{14mu} 1.4}\end{matrix}$And the phase of the SSVEPC is given by ER-SSVEPC

$\begin{matrix}{\phi_{g,{e\; 1},{e\; 2}} = {{Tan}^{- 1}\left( \frac{{Im}\left( H_{g,{e\; 1},{e\; 2}} \right)}{{Re}\left( H_{g,{e\; 1},{e\; 2}} \right)} \right)}} & {{Equation}\mspace{14mu} 1.5}\end{matrix}$

In this case, the coherence across trials in a particular task can becalculated. This yields coherence as a function of time. Thenomenclature can be generalised to take into account multiple tasks andmultiple electrodes.C_(g,d,e,n)=(a_(g,d,e,n),b_(g,d,e,n))where

-   -   g=the task number    -   d=the trial within a particular task, eg a specific response    -   e=the electrode    -   n=the point in time        The following functions are defined:

$\begin{matrix}{\gamma_{g,{e\; 1},{e\; 2},n} = \frac{H_{g,{e\; 1},{e\; 2},n}}{T_{g,{e\; 1},{e\; 2},n}}} & {{Equation}\mspace{14mu} 1.6} \\{H_{g,{e\; 1},{e\; 2},n} = {\sum\limits_{d = 1}^{d = D}{C_{g,{e\; 1},d,n} \cdot C_{g,{e\; 2},d,n}^{*}}}} & \; \\{and} & \; \\{\left. {T_{g,{e\; 1},{e\; 2},n} = {\sqrt{\left( {\sum\limits_{d = 1}^{D}{C_{g,{e\; 1},d,n} \cdot}} \right.}C_{g,{e\; 1},d,n}^{*}}} \right)\left( {\sum\limits_{d = 1}^{D}{C_{g,{e\; 2},d,n} \cdot C_{g,{e\; 2},d,n}^{*}}} \right)} & {{Equation}\mspace{14mu} 1.7}\end{matrix}$The SSVEPC is then given by

$\begin{matrix}{\gamma_{g,{e\; 1},{e\; 2},n}^{2} = \frac{{H_{g,{e\; 1},{e\; 2},n}}^{2}}{T_{g,{e\; 1},{e\; 2},n}^{2}}} & {{Equation}\mspace{14mu} 1.8}\end{matrix}$And the phase of the SSVEPC is given by

$\begin{matrix}{\phi_{g,{e\; 1},{e\; 2},n} = {{Tan}^{- 1}\left( \frac{{Im}\left( H_{g,{e\; 1},{e\; 2},n} \right)}{{Re}\left( H_{g,{e\; 1},{e\; 2},n} \right)} \right)}} & {{Equation}\mspace{14mu} 1.9}\end{matrix}$

The above equations apply to scalp recorded data as well as brainelectrical activity inferred at the cortical surface adjacent to theskull and deeper such as the anterior cingulate cortex. Activity indeeper regions of the brain such as the anterior cingulate orventro-medial cortex can be determined using a number of availableinverse mapping techniques such as BESA (Scherg M, Ebersole J S., BrainSource Imaging of Focal and Multifocal Epileptiform EEG Activity.Neurophysiol Clin. 1994 January; 24(1):51-60); LORETA (Pascual-MarquiRD, Esslen M, Kochi K, Lehmann D. Functional Imaging with Low-ResolutionBrain Electromagnetic Tomography (LORETA): A Review. Methods Find ExpClin Pharmacol. 2002; 24 Suppl C:91-5); or EMSE Information (SourceSignal Imaging Inc. 2323 Broadway, Suite 102, San Diego, Calif. 92102).

While the subject 6 is performing the cognitive and emotional tasks, thevisual flicker is switched on in the visor 8 and brain electricalactivity is recorded continuously on the computer 2.

At the end of the tests, the SSVEP responses associated with the varioustasks can be calculated and separately averaged. For specific tasks, theSSVEP amplitude, phase and coherence can be compared with a database ofresults for groups of subjects with high aptitude and specific thinkingstyles. The comparison will identify the individuals specific thinkingstyle and aptitude. For example, individuals with an aptitude forcomputer software development may demonstrate increased SSVEP phase lagat prefrontal sites and reduced left frontal SSVEP coherence whileperforming Raven's Progressive Matrices (a task used in IQ tests). Bycontrast, an individual suited as an aircraft pilot may demonstratereduced left temporal SSVEP coherence when performing the mentalrotation task. For security purposes, the database can be situated on aremote computer (not shown) accessed via the internet through a modem12.

EXAMPLE 1

The system illustrated in FIGS. 1 to 3 was used for testing subjectsusing an analytical test known as the Hidden Figures Test. Data from theelectrode sites was analysed using the SSPT technique based on computeralgorithms listed in Equation 1.1 and the SSVEP phase distribution wasdisplayed graphically.

FIG. 4 illustrates the SSVEP phase from a subject having high analyticalaptitude. In this Figure, the lighter areas represent SSVEP phaseadvance or regions of increased brain processing speed. In this diagram,the darker shades represent SSVEP phase lag or regions of reduced brainprocessing speed. The light area 50 delineated in broken linesdemonstrates and area of greater activation. This area is situated inthe posterior left hemisphere in the region of the temporal and parietelcortex. This indicates that the subject has a high analytical aptitude.

FIG. 5 graphically represents the SSVEP phase distribution for a subjectcarrying out the same test. It will be noted that there are no lightareas in the distribution and this distribution is interpreted asdemonstrating that the subject has low analytical aptitude.

EXAMPLE 2

The same equipment was used as in Example 1 above but the subjects weremade to perform the Gestalt Completion Test. The Gestalt Completion Testplaces demands on holistic thinking. Electrical activity from theelectrode sites was analysed using the SSPT technique based on computeralgorithms listed in Equation 1.1 and the results displayed graphically.

FIG. 6 diagrammatically shows SSVEP phase distribution. The resultsinclude a light area 52 bounded by broken lines. This light areademonstrates increased activity in the right temporal and right frontalareas which is consistent with the importance of right hemisphereactivity in holistic recognition. This is interpreted as indicating thatthe subject has high holistic thinking ability.

FIG. 7 in contrast shows the results of a subject performing the sametest for a subject having low holistic thinking abilities. The SSVEPphase distribution shows reduced left temporal activity and enhancedleft parietal, left posterior activity as indicated by the light area 54bounded by broken lines.

EXAMPLE 3

The system shown in FIGS. 1 to 3 was used to test subjects carrying outa computerised version of Raven's Progressive Matrices. Electricalactivity was again processed using the SSPT technique based on computeralgorithms listed in Equation 1.8. The results are displayed graphicallyin FIGS. 8 and 9.

The graph of FIG. 8 shows event related SSVEP coherence between activityrecording sites 56. The display includes a plurality of lines 58 betweenfrontal sites. This result was produced from statistically significantdifferences in event related SSVEP coherence recorded from participantshaving high verbal IQ scores.

FIG. 9 graphically illustrates statistically significant differences inevent related SSVEP coherence recorded from participants having highconceptual and visualisation skills (performance IQ). The resultsgraphically shown in FIG. 9 include lines 60 demonstrating increasedevent related SSVEP coherence between right parieto-temporal regions andother scalp sites. The activity was measured whilst the subjects werepreparing to make decisions while undertaking a computerised version ofRaven's Progressive Matrices.

With the techniques of the invention, by examining the scalpdistribution of the SSVEP phase and amplitude and SSVEP event relatedcoherence during a range of thinking tasks and by comparing thesedistributions with a database of known SSVEP amplitude, phase andcoherence patterns, it is possible to infer the aptitude of a specificparticipant to various tasks.

Many modifications will be apparent to those skilled in the art withoutdeparting from the spirit and scope of the invention.

1. A method of assessing the cognitive aptitude of a subject to apredetermined task, the method including the steps of: (i)simultaneously presenting to the subject one of a group of cognitivetasks and a visual flicker; (ii) detecting brain response signals fromthe subject during presentation of said cognitive task and visualflicker; (iii) calculating amplitude, phase and/or coherence of SSVEPresponses elicited by the visual flicker from said brain responsesignals; and (iv) comparing said SSVEP responses to known SSVEPresponses obtained from individuals with high and/or low aptitudes tosaid predetermined task in order to assess the subject's aptitude forsaid predetermined task.
 2. A method as claimed in claim 1 whereinincluding the step of presenting said group of cognitive tasks to saidindividuals in order to obtain said known SSVEP responses and storingsaid known SSVEP response in a database.
 3. A method as claimed in claim1 or 2 wherein the cognitive tasks are selected so that they placedemands on the subject which are similar to demands experienced whencarrying out the predetermined task.
 4. A method as claimed in claim 3wherein the cognitive tasks are selected so that they place one or moreof the following demands on the subject: attention, analytical thinking,holistic thinking, verbal thinking, visuo-spatial thinking, workingmemory, recognition memory and identifying emotional expressions.
 5. Amethod as claimed in claim 1 including the steps of: repeating thepresentation of said cognitive tasks in order to calculate multipleSSVEP responses; statistically analysing said SSVEP responses in orderto determine statistically significant changes in SSVEP amplitude, phaseand/or coherence; and comparing said statistically significant changesto said known SSVEP responses in order to assess the subject's aptitudefor said predetermined task.
 6. A method as claimed in claim 1 whereinthe step of comparing said SSVEP responses to known SSVEP responsesincludes the step of assessing the subject's thinking style.
 7. A methodas claimed in claim 1 wherein steps (i), (ii) and (iii) are performed ata local site and wherein step (iv) is performed at a remote site.
 8. Amethod as claimed in claim 7 including the step of maintaining adatabase of said known SSVEP responses at said remote site.
 9. A methodas claimed in claim 8 including the step of communicating the amplitude,phase and/or coherence SSVEP responses from the local site via theInternet to said remote site.
 10. Apparatus for assessing the cognitiveaptitude of a subject to a predetermined task, the apparatus including:(i) means for simultaneously presenting to the subject one of a group ofcognitive tasks and a visual flicker; (ii) means for detecting brainresponse signals from the subject during presentation of said cognitivetask and visual flicker; (iii) means for calculating amplitude, phaseand/or coherence of SSVEP responses elicited by the visual flicker fromsaid brain response signals; and (iv) means for comparing said SSVEPresponses to known SSVEP responses obtained from individuals with highand/or low aptitudes to said predetermined task in order to assess thesubject's aptitude for said predetermined task.
 11. Apparatus as claimedin claim 10 wherein said means for presenting, said means for detectingand said means for calculating are located at a local site and saidmeans for comparing is located at a remote site and wherein theapparatus includes coupling means for coupling said means forcalculating to a communications network for transmitting said SSVEPamplitude, phase and/or coherence responses to said means for comparingvia the network.
 12. Apparatus as claimed in claim 11 wherein thecoupling means includes a modem and the network is the Internet.